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Transferring Tray Drying to Fluid Bed Drying

Apr. 13, 2022

Nowadays, there is a wide range of different Pharmaceutical Tray Dryers available in the market that can effectively help you to reduce wastage and increase productivity. They are specifically designed to reduce the heat generated by the heating system in the laboratory by more than 60 percent. The drying temperature is increased to maintain the purity of the substances being tested or manufactured. This results in the quick drying of the sample or compound by preventing it from breaking down during the heating process.


Pharmaceutical Tray Dryer has many benefits.

Pharmaceutical Tray Dryer with Electrical Hot Air Heater base has many benefits. The foremost benefit is that it facilitates quick drying of chemical substances without increasing the temperature of the samples. When the compound is heated, it usually breaks down into small particles that escape out through the vents or escape with the help of steam vapor. Hence, it is important to have good quality trays for continuous drying. This can be effectively achieved with the help of electrical heating systems.


Two types of Tray Dryers

There are two main types of Tray Dryers available in the market that includes the electric base and the manual base. The electric base is the one which is commonly found in the laboratories. It is generally placed on the table or shelf directly facing the steam source. The Electric Tray Dryer consists of multiple nozzles that are positioned in various locations of the industrial area. This is the most suitable type for hot room applications as it has adjustable nozzles that can be manually set according to the steam temperature.


Manual Tray Dryers, on the other hand, are not commonly used in the laboratories due to the difficulty in accessing them and the need for additional equipment for steam base drying. But they are useful when it comes to drying solid materials such as drugs. They are placed in the pharmaceutical lab area next to the workstations so that the workers can easily access them for drying. However, it is important to regularly adjust the temperature of the tray dryers since prolonged exposure to high temperatures can result in the contamination of the substance inside the bottle.


Using tips

In order to regulate the drying speed of the Tray Dryer, it is advisable to maintain a certain amount of water in the container. This can be done by regularly adding water to the container. Also, make sure that the drying agent used is strong enough to dry all the solid stuff placed in it. Some common drying agents used in the dryers are glycerol, methanol and alcohol. A good quality drying agent also ensures faster drying speed.

Lastly, always choose the heating system that offers you the best options such as automatic or manual operation. Both types of drying equipments are highly effective and can dramatically reduce waste in the production process. However, if you are looking for maximum drying speed then it is better to opt for automatic Tray Dryers. For manual equipment, dryers that are heated by gas flames will perform best.

Transferring Tray Drying to Fluid Bed Drying

Granulation is an integral part of solid dosage manufacturing in the pharmaceutical industry. The majority of the granulation process uses a liquid binder to granulate the product in the mixer and then a tray dryer or a fluid bed dryer. A number of products that received FDA approval in the early days use tray dryers and are considering transferring to fluid bed. Besides FDA requirements and other financial and engineering considerations, maintaining the final product attributes is most crucial. We must understand the differences in the two types of dryers and the impact it may have on the quality of our product after such a transfer.

Solids drying involves two fundamental processes. Heat is transferred to the granule to evaporate liquid, and mass is transferred as a liquid or vapor within the solid and as vapor from the surface into the surrounding gas phase. The factors that influence the rates of these processes determine the drying rates.

Transferring Tray Drying to Fluid Bed Drying

FG series fluid-bed dryer


For tray drying, the wet mass is spread on to trays and the tray rack is then placed in the oven. The heat transfer is accomplished by direct contact between the wet solids and hot gases. The vaporized liquid is carried away by the drying gases. There is no relative motion among solid particles. The solids bed exists as a dense bed, with particles resting upon one another, and experiencing no relative motion among them. Depending on the quantity and the type of solvent used, it may take anywhere from a few hours to 24 hours to dry the product.

In the case of fluid bed drying, the particles are suspended in a hot gas/air stream. The heat transfer is accomplished by direct contact between the wet solids and hot gases. The vaporized liquid is carried away by the drying gases. The solids are in expanded condition, with the particles supported by drag forces caused by the gas phase. The solids and gases intermix and behave like a boiling liquid. The drying time could be 30-90 minutes.


The possibility of having color migration and case-hardening of tray dried is quite common. The processing of dried granules by milling and subsequent compression should be investigated to make sure the critical product attributes are identified and monitored during the transfer of product from tray drying to fluid bed drying. While using a fluid bed dryer, it is advisable to pass the wet mass through a coarse screen, so cohesive chunks of product can be subdivided into free-flowing granules that will improve process efficiency.


The combination of the granulating solvent and drying conditions could result in the conversion of some of the products to alternate crystalline forms during the drying process as presented in a case study, Drying of Glycine and Microcrystalline Cellulose (1:1 - one part of glycine and one part of microcrystalline cellulose - i.e. 50% of each ingredient). The study compared aqueous granulation in a fluid bed unit as well as in a tray dryer. Using near infra red, the researcher concluded that the slower drying techniques, such as tray drying, resulted in significantly less formation of Alpha-glycine - a polymorph. The drying rate determined the overall polymorph content. The faster the granulation was dried, the more rapid the increase in super saturation with respect to the metastable form and the greater thermodynamic driving force for the nucleation and crystallization of the metastable form. The granulation rapidly dried by fluidized bed drying, resulted in more crystallization of Alpha-glycine than the granulations that were tray dried.


In summary, while considering product transfer from tray drying to fluid bed one needs to understand the equipment differences, drying kinetics, capital cost, and space requirements, while assuring that the product attributes have not changed.


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